Many processes and devices have been utilized for sensing pressure, temperature, speed, direction, etc., in different applications. Often, requirements exist for measuring these conditions over an extensive range. For example, a highly sensitive pressure sensor, inherently used for measuring low range pressure, is delicate and prone to destruction when subjected to an overload pressure. Conversely, sensors characterized by necessary stiffness to accurately measure high range pressure are insensitive and thereby inaccurate within low pressure ranges. Similarly, pressure responsive devices such as strain gauges and diaphragm capsules linked to dial indicators can be sufficiently strong to measure over extensive pressure range, but are not sensitive enough to accomplish accurate measurements in low pressure ranges.
Although the present invention can be used for various sensors, pressure will be discussed as an exemplary application for the present invention. Pressure is not meant as, and should not be interpreted as, a limitation over the scope of the present invention. The majority of prior art pressure sensors typically include a thin silicon diaphragm which can be stressed in response to an applied pressure. The stress can be measured by piezoresistive elements formed in a diaphragm. The thickness of the diaphragm can be a function of the range of pressure being sensed. Fabricating multiple piezoresistive elements for responding to different pressure ranges is undesirable. Such devices cannot ensure a high level accuracy and internal reliability during extensive pressure range.
There has been an increased demand for a pressure sensor with improved capabilities across a large pressure range. Instead of employing two separate sensors, the industry has widely adopted pressure measuring instruments which can combine both capabilities into a single, unitary element.
In the industry today, pressure sensors which provide dual functions, a sensor which can measure across a large pressure range, are preferred by the users. To meet this need and reduce the financial strain of delivering smaller and smaller accuracy tolerance, a dual range ASIC could be used. An example of an application of this type of ASIC is in an automotive engine lubricating oil system. Currently, the OEMs (Original Equipment Manufacturers) are utilizing oil pressure switches to monitor the oil pressure and ensure that it does not drop below a certain threshold. As the OEM's move to more modern systems of controlling their engines, for instance variable valve timing or cylinder deactivation systems, they need to get the continuous oil pressure. This translates into a high demand for a sensor, which can accurately measure the low-pressure range and then transition to a lower accuracy for higher pressures. In order to provide optimized utilization of pressure sensors across the large pressure range, a dual range ASIC (Application specific integrated chips) can be used which offers high-end accuracy and relatively high precision.
Based on the foregoing, it is believed that the preferred dual range sensor incorporating ASIC can therefore provide an improved sensor for applications requiring input in pressure, speed, temperature and direction, which could accurately measure the input over an extensive range, precisely at the lower range.